The disclosed invention relates to a control that is operable at transient conditions to reduce pressure spikes in a refrigerant circuit incorporating a microchannel heat exchanger. In particular, the disclosed invention relates to a control that is operable at transient conditions to reduce pressure spikes in a refrigerant circuit incorporating a microchannel condenser or gas cooler.
In recent years, much interest and design effort has been focused on efficient and durable operation of the heat exchangers in refrigerant systems. One relatively recent advancement in heat exchanger technology is the development and application of parallel flow, or so-called microchannel or minichannel, heat exchangers (these terms will be used interchangeably throughout the text), as the indoor and/or outdoor heat exchangers.
These microchannel heat exchangers are provided with a plurality of parallel heat exchange tubes, typically of a non-round shape, among which refrigerant is distributed and flown in a parallel manner. The heat exchange tubes typically incorporate multiple channels and are orientated generally substantially perpendicular to a refrigerant flow direction in inlet, intermediate and outlet manifolds that are in flow communication with the heat exchange tubes. Heat transfer enhancing fins are typically disposed in between and rigidly attached to the heat exchange tubes. The primary reasons for the employment of the microchannel heat exchangers are related to their superior performance, high degree of compactness, structural rigidity, reduced refrigerant charge and enhanced resistance to corrosion.
Microchannel heat exchangers provide beneficial results, at least in part, because their internal flow channels are of quite small hydraulic diameter. However, there are also challenges associated with microchannel heat exchangers related to their small hydraulic diameter and substantial reduction in internal volume as compared to the conventional type of heat exchangers. One challenge is that a microchannel condenser or gas cooler is susceptible to pressure spikes at start-up or other transient conditions, such as operational regime changes.
When pressure spikes occur in such a refrigerant system, they can lead to nuisance shutdowns and eventually to an inability to control environmental parameters, such as temperature and humidity, in the space to be conditioned.